High genomic variability predicts success in desert tortoise refugees; could inform conservation

Tortoise refugees with the highest genetic variation are far more likely to survive conservation translocation than tortoises whose genetic diversity is lower, according to a new study. The findings suggest that translocation efforts should account for genetic variation when selecting target individuals rather than focusing solely on those determined to be most geographically or genetically similar to the target populations. Human activity and climate change are driving record numbers of species towards extinction and represent a challenge that is being addressed by a myriad of conservation efforts worldwide. One conservation strategy employed to preserve threatened species is through translocation of individual plants and animals to areas where they’ve become locally extinct or to new locations where they might bolster declining resident populations. While the approach is becoming increasingly common, it is often reserved as a last resort as the long-term success is often quite poor. An ongoing debate in this area relates to whether such efforts are most successful when they target individuals from environmentally similar regions or genetically close target populations, or when they focus on overall genetic diversity. To test these hypotheses, Peter Scott and colleagues used a long-term dataset of displaced Mojave Desert Tortoises – many previously captive pets – brought to the Desert Tortoise Conservation Center’s translocation site in Nevada. Scott et al. analyzed genomic data for 166 desert tortoise refugees that either survived or died over a period of twenty years and found that neither geographical distance nor genetic similarity had any effect on post-translocation survival. Instead, the greatest predictor for success was heterozygosity – individuals with the highest genomic variation survived at much higher rates than others. While the authors note that further research is needed to understand the reasons behind this increased survival, the new insights suggest ways to improve current translocation efforts.